I saw this article and would like to try this technique for fun.
Does anyone know how it was done? It might be a nice way to add color
to silver pieces.
Gerald A. Livings
I saw this article and would like to try this technique for fun. Does anyone know how it was done? It might be a nice way to add color to silver pieces.
http://www.ganoksin.com/gnkurl/ep81mm
Isn’t this gild depletion?
Lorraine
Same principle as repeatedly quenching hot sterling in pickle to
yield a thin fine silver surface, so probably not quite as "secret"
as the newspaper writers suggest.
Cheers
Hans Durstling
Moncton, Canada
now that sounds like FUN lol 25% low grade gold perhaps a look on
the English historical site will give you a way to contact them and
ask about the technique
Teri
Sounds like plain old depletion gilding. not much of a
’secret’…:-)…
The article says: at the surface the silver leached out and could be
burnished off.
"Burnishing off’ is an oxymoron… burnishing doesn’t remove
material, quite the opposite, it ‘presses’ the material
in…:-)…!
Janet in Jerusalem
It may be the same process that the Pre-Columbian metalsmiths used
called ‘Tumbaga’. It’s an alloy that by depletion gilding it, you
can raise the gold to the surface. As little as 12% gold by weight
can result in a beautiful rich gold color.
See Tim McCreight’s book Metals Technic, for the article written by
Kris Patzlaff with instructions on how to achieve the the result
that you may looking for.
Vicki
Gerald, Sir Leonard Woolley commented on some Sumerian pieces from
Ur, with more gold on the surface than in the interior. He suggested
that they had been soaked in beer, which would dissolve silver from
the surface. Then the surface would be burnished and appear to be
high-grade gold.
Check out the Orchid Archives for an earlier discussion of this
issue.
Judy Bjorkman
Owego, NY
Hi Gerry,
It’s probably just depletion gilding. (Heat to oxidize the surface
silver, etch off the oxidized silver. Rinse. Repeat. A lot.)
The description in the article is flatly wrong in at least one
respect. (“burnishing” the excess silver off. Etching it off maybe,
but not burnishing.) The final stage of depletion gilding is
burnishing to consolidate the surface, so that may be where the
’burnishing’ error comes from.
That error makes me question everything related to that process
description. If it was mentioned by the Romans, I’d dig around in
Pliny. That seems to be where a lot of that info comes from. I can’t
remember anything in Pliny off hand that would give that effect, but
it’s been a great many moons since I read Pliny. I’ll go look again.
Now that I’ve been poked, I’ll do some digging, and see if I can get
the original paper, or some sense of what’s going on.
Regards,
Brian
Hmmmm. Never heard of this technique. However mercury gilding has
been around since the 4th century BC.
James Binnion- You know the answer to this? You da smarty pants
metals
Jo Haemer
timothywgreen.com
nitric will eat silver but not gold, In ancient peru they had
Tumbaga and tumbaga had a bit of gold but was mostry copper and siler
ore (electrum) they "depleted copper and sile by bilig amazonias acid
plats, burnishon and repeating till they got the fine gold layer.
turn out the Spanyards would be very dissappointed when they melted
it
Alberic/Brian:
Yes, this is like Pliny’s cementation process (1st century AC):
Impure gold placed in crucible in intimate contact with a mixture of
salt and brick dust. Heat. Base metals and silver get absorbed in
brick dust, leaving behind relatively pure gold which is separated
from brick dust by washing.
In the early 1970’s J. H.F Notton followed the methods described by
Agatharchides (Greece, 2nd BC.) and Pliny and the results: 9K
gold/silver alloy left a 93% gold residue! - Gold Bulletin Vol. 7
Issue 2.
Also see: “Pliny the Elder on Gilding” Gold Bulletin Vol 12 Issue 1
p.35
For those of you who want to try it, best source on subject: Heather
Lechtman on the pre-Columbian goldsmiths of Central and South
America:
“The gilding of metals in Pre-Columbian Peru” Lechtman, Heather
(Proceedings of the 3rd Seminar (1970) on the Application of Science
in the Examination of Works of Art, Museum of Fine Arts, Boston,
1973, Edited by Young, William J.)
“Ancient Methods of Gilding Silver”, H. Lechtman, Science and
Archeology, ed. R. H. Brill
Also “The Art of Depletion Gilding”, Del Solar and Grimwade, AURUM
#12
Janet in Jerusalem
I have read that the pre-Colombian technique was done on pieces with
as little as 3% gold, but with enough patience, the surface is pure
gold. I have experimented a little myself, alternately heating then
pickling (to remove copper) and soaking in nitric acid (to remove
silver), starting with 14k. It seemed to me that it worked!
Noel
“Gold War: The Lost Gold Mines of Canada’s Mountain Indians” is in
press (Xulon, Florida) and we are now doing the proof reading/fine
tuning. Much of it has to do with how gold is concentrated in nature
as for this Orchid report/thread on “depletion gilding”. I had to
conclude in overview that there is far, far more about gold that we
do not know compared to what we know. Chapter 14 titled "Goldfish"
presents assay results on the shells of shell fish (clams and snails)
from a high gold bearing region.
The shells are disproportionately high in gold and high also in only
two other elements among the 53 of the assay profile: strontium and
bismuth. Excellent work by Acme Assayers, as always. Irrefutably the
shell fish are mining and concentrating a gold (alloy?) product. One
must wonder how creatures which make mineral-like parts of their
bodies (like molluscs and diatoms) and even form the gold-bearing
structures using their DNA-RNA. Other questions which arise: Would
you call the gold- ____? in the shells an alloy (biologically made)?
Of course calcium is a mainstay of the assay. Is gold-calcium an
alloy? Can it be used as a tracer/vector to find gold mother lodes?
Is gold alloying related to shell colour since the clams have an
excellent pinkish-green “mother of pearl” gloss and the snails are a
subdued red and yellow? Does anyone on Orchid know of other shell
fish assays? What about bones of fin fish in higher gold content
waters? We use fine gold/flour gold tracers in streams to find source
lodes (mother lodes). Can fin fish also give us vectors?
M
Thank you for all of the advice and links. I have enough to play and
learn this now. =)
Gerald A. Livings
As Noel says, gold “mixtures” with other metals can be very low. My
question has to do with whether all such mixtures are alloys? That
being so do the clams and shells assayed for the book “Gold War”
(Rock Hunter, Xulon/Florida, 2014, in press) actually create
biological alloys? That is quite amazing is it not since we think of
alloys as requiring much heat and/or pressure. In Gold War, there is
also a note on the Royal Bank of Canada Tower in Toronto which has
small (in ppm or ppb) amounts of gold mixed with silica (in total
worth millions). Is that an alloy? Some time ago I also posted to
Orchid on another of my “crazy assays”. I had discovered tiny golden
specks in the hair-thin slickening of fractured rock faces on one of
my gold claims. So I painstakingly ground off enough of this crystal
clear glassy material where there was NO visible gold. I got
surprisingly high gold assays. Is that a silica-gold alloy given that
the petrographic report done by a reputable local geologist said this
was a formation of metamorphic mantle-source rocks subjected to much
heat and pressure in more recent geological times. Also one might
expect some diatoms with silica shells to be alloys if the clam and
snail shells are alloys. Opinions appreciated - it is still not too
late to put them in the book.
alloys arespecific to metals, mixtures can be anything. As for gold
in clam shells that can be disseminated precipitates. Gold on
slickensides in fault rocks is quite common, it is all to do with
heat and pressure and best plotted by looking for other minerals
that have known temperature or heat specific boundaries for formation
such as sphalerite and fluid inclusions in quartz.
when you find particles of gold that are less than a couple of
microns across they do not look like gold.
nick royall
Hi Peter
from emporis dot com - they say it is a coating and that is what I
was told too as I watched the building going up in toronto Facts
-
The two Royal Bank Plaza towers are connected by a 39-meter (130
foot) tall glass Banking Hall. -
All 14,000 windows of the towers are coated with a layer of
24-karat gold (2,500 ounces or 70,875 grams), worth about $70 per
window. The total amount of gold used in the windows is just over
$1,000,000. -
Not only does this gold give the buildings a particular look
(especially in sunlight), it also reduces heating bills, as gold is
an excellent insulator. The manufacturing process for the glass has
made the gold non-recoverable.